I. Effects of phosphorylation on regulation of aminoacylation. A. Examine the effects of phosphorylation in vivo and in vitro on aminoacyl-tRNA synthetase activities including aminoacylation, tRNA binding, synthesis of Ap4A, and complex association/dissociation. B. Compare the sites phosphorylated in vivo in response to hormones/TPA to those phosphorylated in vitro with purified protein kinases. C. Analyze the site-specific phosphorylation of eight synthetases in the high molecular weight complex and threonyl-tRNA synthetase in response to hormones and the tumor promoting phorbol ester, TPA, In Reuber H35 rat hepatoma cells and reticulocytes. D. Examine the remaining synthetases to determine whether they are phosphorylated. Those of interest will be examined in detail as described in A-C. II. Examine the effects of the site-specific phosphorylation of S6 by the cAMP-dependent protein kinase and PAK II on regulation of protein synthesis. A. Examine the effects of the site-specific phosphorylation of S6 on protein synthesis in a reconstituted protein synthesizing system using selected messages. B. Examine the effects of phosphorylation of S6 on binding of mRNA, binding of aminoacyl-tRNA, and binding of met-tRNAi. C. Compare changes in the site-specific phosphorylation of S6 in response to various hormones/TPA with changes in protein synthesis.